Aqueous dispersions formed by dispersing hydrophobic amino resin in aqueous medium in the presence of water-soluble resin as a dispersion stabilizer, have been generally used in the field of paints. As water-soluble resins for preparing these aqueous dispersions, conventionally acrylic resin, alkyd resin, epoxy resin and the like which contain hydrophilic groups such as carboxyl, amino and the like groups are used.
Those aqueous dispersions are subject to such problems as insufficient storage stability under room temperature or elevated temperatures or notable viscosity change under mechanical load which, when the dispersions are used for making water-based paint, deteriorate the coating film performance, e.g., water resistance, and/or aggravate finished appearance of the coating film, due to poor dispersion of the amino resin.
Water-based paint compositions in which polyester resins of specific composition containing aromatic polybasic acid, ethylene glycol and the like as the essential monomeric components are used as a dispersion stabilizer for hydrophobic amino resin have also been proposed (e.g., see JP Hei 11(1999)-124542A). Such water-based paint compositions, however, are subject to a problem that a large quantity of the polyester resin is required for dispersing the amino resin in water, which invites a drawback that the paint compositions come to have high viscosity.